By Alexey Spasskiy · Published April 2, 2026 · Updated June 8, 2026 · 7 min read
Quick Answer: Electronic fax (eFax) lets you send and receive faxes over the internet from any device — no fax machine, no phone line, no paper required. Services like mFax make it as simple as attaching a file to an email.
If you've ever needed to send a fax and ended up driving to a UPS Store, you already understand the problem that electronic fax solves. eFaxing — also called internet fax or online fax — replaces the hardware and the phone line with an internet connection. The document still arrives at a real fax number. The process just no longer requires you to be standing next to a machine.
This guide explains what electronic fax is, how it works technically, how it compares to traditional faxing, and how to send your first fax electronically in under two minutes.
What Is Electronic Fax?
Electronic fax is a technology that transmits documents to fax numbers over an internet connection instead of an analog telephone line. You send a digital file — a PDF, a scanned image, a Word document — through a web app, email, or mobile app. The service converts and delivers it to the recipient's fax number, whether that number belongs to another online fax service or a traditional fax machine in a doctor's office.
The critical point: an electronic fax number is a real fax number. Anyone can send to it. Anyone can receive from it. The conversion between internet data and the telephone network's fax signal happens invisibly on the provider's servers. From a compatibility standpoint, eFax and traditional fax are interchangeable.
eFax vs. Internet Fax vs. Online Fax
These terms are used interchangeably. "eFax" is also the name of a specific service, but in general usage it refers to any electronic fax technology. Our internet fax guide covers the full landscape of providers.
How Does Electronic Fax Work?
When you send an electronic fax, four things happen in sequence:
1. Document preparation. Your file is formatted and compressed to the T.30 or T.38 fax protocol standard — the same encoding a physical fax machine would use.
2. Encryption. Before transmission, the file is encrypted using TLS (Transport Layer Security) for transit and AES-256 at rest. This is the same encryption tier used by online banking.
3. Transmission. Instead of audio tones over a copper phone line, your document travels as data packets across the internet to the provider's servers. Those servers bridge to the public switched telephone network (PSTN) and deliver the signal to the destination fax number.
4. Delivery and confirmation. The recipient's machine (or online fax inbox) receives the transmission and prints or saves the document. The provider sends you a delivery receipt confirming the fax was accepted.
Receiving works in reverse: an incoming fax signal arrives at the provider's gateway, gets converted to a PDF, and lands in your email inbox or in-app message center.
No busy signals, no waiting
Because your fax travels over the internet rather than a single phone line, you can send and receive multiple faxes simultaneously. Busy signals are eliminated entirely.
Types of Electronic Fax Services
Electronic fax comes in three delivery formats. All of them use the same underlying technology — only the user interface differs.
Email-to-Fax
Compose a regular email, attach your document, and address it to [fax-number]@[provider-domain]. The service converts the attachment and delivers it as a fax. Incoming faxes arrive as PDF attachments to your inbox. No new software required — works with Gmail, Outlook, Apple Mail, or any email client.
Web Portal
Log into a browser dashboard, upload your file, enter the recipient's fax number, and click send. This method gives you the most control over each transmission and is best for occasional senders who want a clear paper trail per fax.
Mobile Fax App
Download a dedicated app to your iPhone or Android. You can photograph a paper document with your phone's camera, upload a PDF from cloud storage, or pull a file from your photo library — then send it as a fax in seconds. This is the fastest option for mobile workflows. mFax uses this format, letting you send from anywhere in under two minutes.
For enterprise teams that need shared inboxes, multiple user accounts, and centralized management, a cloud fax service adds those capabilities on top of the same core technology.
How to Send a Fax Electronically
Choose an electronic fax service
Sign up for a provider that fits your volume. mFax lets you pay per fax with no subscription — ideal if you send occasionally. You'll receive a real fax number assigned to your account immediately.
Prepare your document
Upload a PDF for the cleanest rendering at the recipient's end. If your file is a Word document, image, or scan, most services convert it automatically. Need to convert first? The free mFax document converter handles it without signup.
Enter the recipient's fax number
Type the full fax number including country code (e.g., +1 for the US). Double-check before sending — fax numbers don't auto-correct the way email addresses can. A wrong digit means a failed delivery or, worse, the document arriving at the wrong place.
Send and confirm
Click Send. Within seconds, your provider processes and transmits the document. You'll receive a delivery confirmation — a transmission report showing the time, recipient number, and delivery status. Keep this as your proof of sending.
Electronic Fax vs. Traditional Fax
| Factor | Traditional Fax | Electronic Fax |
|---|---|---|
| Hardware required | Fax machine ($100–$500) | None — any device with internet |
| Phone line | Dedicated analog line (~$40/mo) | Not required |
| Monthly cost | $50–$100+ (line + supplies) | $8–$25/mo or pay-per-fax |
| Mobility | Office-only | Send from anywhere |
| Simultaneous faxes | One at a time per line | Unlimited |
| Document storage | Paper filing cabinets | Cloud inbox, searchable |
| Busy signals | Yes | No |
| HIPAA compliance | Partial (no encryption) | Yes, with BAA |
The numbers make the case clearly. A traditional fax machine setup runs $50–$100+ per month once you add the dedicated phone line, paper, toner, and occasional maintenance. Electronic fax services start at $8–$25/month — or less if you pay per fax rather than subscribe. See the best free online fax services for options with no monthly fee.
The bigger advantage is mobility. A fax machine requires you to be physically present in the room where it's installed. Electronic fax works from any device, anywhere with internet access — your phone on a commute, a hotel laptop, or a tablet between meetings.
Is Electronic Fax Secure?
Yes — electronic fax is more secure than email and on par with online banking. Here's the breakdown:
- Encryption in transit: TLS encrypts your document as it moves from your device to the provider's servers and across the network to the destination.
- Encryption at rest: AES-256 protects stored faxes — the same standard used by the US military and financial institutions.
- Immutable documents: A received fax is a fixed image. Unlike email attachments, the document cannot be altered after transmission, which matters for legal and evidentiary purposes.
- Delivery receipts: Every fax generates a transmission record confirming exactly when the document was received and by whom.
- No interception risk from phone taps: Analog fax signals on phone lines can be intercepted with physical access to the line. Encrypted internet fax traffic cannot be read even if intercepted.
HIPAA compliance needs a BAA, not just encryption
For healthcare providers, encryption alone is not enough. HIPAA requires a signed Business Associate Agreement (BAA) with any vendor that handles protected health information. See our HIPAA-compliant fax guide for the complete checklist. mFax Business includes a BAA as standard. For a deeper look at fax security, read Is Online Fax Secure?
Who Uses Electronic Fax?
Healthcare is the largest user by volume. US healthcare organizations exchange over 9 billion fax pages annually — medical records, prescriptions, lab results, referrals, and insurance claims. Electronic fax fits this workflow perfectly: it carries the security and legal standing of fax while adding cloud accessibility, audit logs, and EHR integration.
Legal professionals use electronic fax for court filings, signed contracts, and client documents. Courts recognize faxed signatures as equivalent to originals — a status that email still struggles to establish in many jurisdictions.
Small businesses and individuals reach for eFax when dealing with tax documents (the IRS accepts faxed forms), insurance claims, mortgage paperwork, and any situation where a timestamped delivery receipt matters more than a read receipt.
If you've ever needed to fax something and couldn't find a fax machine nearby, you're in the target audience. Electronic fax removes the need to ever locate one again.
Get Started with Electronic Fax
Electronic fax eliminates every friction point of traditional faxing — the hardware, the phone line, the physical presence, the paper — while preserving everything that matters: compatibility with any fax number, legally recognized delivery, and document immutability.
For personal faxing, download the mFax app and send your first fax in under two minutes. Pay per fax with no subscription commitment, or subscribe for regular use. Over 5 million users have already made the switch.
For business teams that need HIPAA compliance, dedicated virtual fax numbers, and shared team inboxes, mFax Business starts at about $9/mo (billed annually) — with a BAA included, audit trails, and multi-user accounts. Instead of rigid fixed tiers, you build your own plan with a live calculator, dialing in the exact seats and pages you need and paying only for what you use.
The fax machine had a good run. You don't need it anymore.